Magnetite (Fe3O4) and Maghemite (&amp / #947 / -Fe2O3) are well-known iron oxide phases among magnetic nanoparticles due to their magnetic properties, chemical stability, and nontoxicity. They have gained acceptance in several fields of application of nanomaterials such as magnetic recording systems, magnetic refrigeration, magneto-optical devices, magnetic resonance imaging, magnetic separation techniques and separation and purification of biological molecules. Recently, there is a growing interest in the synthesis of magnetic iron oxide nanoparticles in a polymeric, glassy or ceramic matrix since the preparation of pure phase iron oxide composite material involves, presently, some difficulties partially arising from different oxidation states of iron which can lead to the presence of various oxides. Matrix support, in principle, modifies the properties of nanomaterials, thus opening new possibilities for the control of their performance. In addition, the chosen matrix, polymer or sol-gel, provides binding of the functional groups and also prevents grain growth and agglomeration. Therefore, extensive research is conducted on this subject. Sonochemical technique is an effective method to synthesize magnetic nanoparticles with many unique properties due to extreme reaction conditions. Besides, a microscopic mixing in the synthesis procedure is obtained because of the microjet effect which comes from the collapse of the bubbles. This effect creates relatively uniform reaction conditions. Thus, well-dispersed and stable nanoparticles are obtained by using ultrasound. In this study, &amp / #947 / -Fe2O3, maghemite nanoparticles are accommodated in an inert, inorganic, transparent and temperature resistant sol gel matrix to achieve stabilization. The nature and concentration of the salt used, evaporation conditions of the sols, the following heat treatments had been investigated and shown that they had great influence on the particle size and the final iron oxide phase in the sol-gel. The Fe2O3/SiO2 nanocomposites were characterized using X-ray diffraction (XRD) and vibrating sample magnetometry (VSM) techniques. In addition, magnetite (Fe3O4) nanoparticles were synthesized via co-precipitation in the presence of poly(methacrylic acid) (PMAA) in aqueous solution. PMAA, which was used as the coating material, prevents magnetite nanoparticles from oxidation towards a lower saturation magnetization iron oxide phases. In order to achieve small particle size and uniform size distribution of the magnetite nanoparticles in PMAA matrix, ultrasonic irradiation was applied during co-precipitation. The polymer coated Fe3O4 nanoparticles were characterized using scanning electron microscopy (SEM), laser particle sizer, X-ray diffraction, (XRD) and vibrating sample magnetometry (VSM) techniques and zeta potential measurements.

Submitted by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T14:00:18Z No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T14:00:27Z (GMT) No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2017-08-22T14:00:33Z (GMT) No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) / Made available in DSpace on 2017-08-22T14:00:38Z (GMT). No. of bitstreams: 1 DissRCG.pdf: 1738048 bytes, checksum: 5fe499e8468dd911a3576a5aaf9afff3 (MD5) Previous issue date: 2017-03-02 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Nanoparticles (NPs) have been produced on a large scale worldwide for various consumer purposes such as the production of cosmetics, sunscreen, biosensors, human prosthetics and cancer therapy. However, due to its large production, NPs can have water bodies as final destination, where current studies addressing these compounds are not sufficient to estimate the threat that these substances could cause to aquatic organisms. Chronic studies with nano-Fe3O4 are scarce and, to the best of our knowledge, inexistent regarding tropical zooplankton species, although chronic studies are of great importance to predict the effects of the substances because they analyses great part of this organisms life cycle. At present study, we investigated nanoparticles of Fe3O4, to the tropical cladoceran Ceriodaphnia silvestrii using acute toxicity tests (0.00; 0.01; 0.10; 1.00; 10.00 and 100.00 mg L-1) during 48h, and chronic toxicity tests (0.00; 3.125; 6.25; 12.50; 25.00 and 50.00 mg L-1) during 14 days. Characterization of NPs in the exposure medium revealed that they experienced agglomeration and aggregation on a micrometer scale. Results showed non-toxicity of nano-Fe3O4 after 48h of acute exposure (EC5048h > 100.00 mg L-1). ). In chronic tests, treatment of 50 mg L-1 caused significant inhibition of growth and reproduction, affecting the maximum length (inhibited 12.71%), accumulated number of eggs (reduction of 51.99%) and neonates (decrease of 61.37%) per female (Dunnett’s test, p < 0.05). We concluded that nano-Fe3O4, in the 14th day, was toxic to C. silvestrii only at the highest concentration tested (50.00 mg L-1) during this chronic exposure.. The use of nano-Fe3O4 in aquatic environments could be considered safe to this species in concentrations up to 25.00 mg L-1, according to the parameters evaluated. / As nanopartículas (NPs) têm sido amplamente produzidas em larga escala para vários propósitos tais como: produção de cosméticos, protetores solares, biosensores, próteses humanas e tratamento do câncer. No entanto, devido à ampla produção, eventualmente as NPs podem encontrar seu destino final nos corpos d’água, onde os estudos relativos à presença dessas substâncias muitas vezes não são suficientes para estimar os efeitos que as mesmas poderiam causar nos organismos aquáticos. Estudos de toxicidade crônica com nanopartículas de óxido de ferro (nano-Fe3O4) são escassos e, até onde sabemos, inexistentes para cladóceros tropicais, embora avaliações crônicas sejam de grande importância para predição dos efeitos de substâncias, pois abrangem grande parte do ciclo de vida dos organismos. No presente estudo, foram estudadas nanopartículas de Fe3O4 para cladócero neotropical Ceriodaphnia silvestrii, por meio de testes de toxicidade aguda (0,00; 0,01; 0,10; 1,00; 10,00 e 100,00 mg L-1), durante 48 horas, e crônica (0,00; 3,125; 6,25; 12,50; 25,00 e 50,00 mg L-1), durante 14 dias. A caracterização das NPs nos meios de exposição revelou que elas sofreram aglomeração e agregação em escalas micrométricas. Os resultados obtidos apontaram ausência de toxicidade aguda para as nano-Fe3O4 (CE(I)5048h > 100,00 mg L-1). Nos testes de toxicidade crônica, no tratamento de 50,00 mg L-1, houve inibição significativa no crescimento e reprodução, afetando o comprimento máximo (inibição de 12,71%) e o número acumulado de ovos (diminuição de 51,99%) e de neonatas (diminuição de 61,37%) produzidos por fêmea (teste de Dunnett p < 0.05). Concluiu-se que as nano-Fe3O4 apresentaram efeitos crônicos, no 14º dia, para o cladócero C. silvestrii somente na maior concentração avaliada (50,00 mg L-1). O uso de nano-Fe3O4 em ambientes aquáticos pode ser considerado seguro para esta espécie de cladócero tropical, com base nos parâmetros avaliados, até concentrações de 25,00 mg L-1. / CNPq: 132379/2015-5 / FAPESP: 2014/14139-3 / FAPESP: 2016/00753-7

Les nanoparticules magnétiques sont de nos jours largement exploitées dans le domaine de la recherche pour le biomédical, pour des applications aussi variées que le diagnostic, la thérapeutique ou plus récemment la théranostique. Les nombreuses méthodes de fabrication mises au point à ce jour permettent l’obtention d’une large gamme de nanoparticules en termes de taille, forme, matériaux et donc propriétés magnétiques. Le procédé de fabrication idéal est celui qui permet la fabrication simple, peu coûteuse et à grande échelle de nanoparticules parfaitement monodisperses. En ce sens, le premier volet de la thèse sera consacré à l’étude d’un nouveau procédé de fabrication basé sur la combinaison d’une approche « top-down » et « bottom-up », qui permet d’obtenir des nanoparticules de dispersion en taille très étroite. L’idée est d’exploiter les propriétés d’auto-organisation d’un copolymère dibloc, dont l’une des deux phases peut s’organiser en cylindres verticaux dans la matrice de l’autre phase sous certaines conditions. La gravure sélective des cylindres mène à l’obtention d’un masque de trous dans une matrice de polymère. On peut ensuite déposer le matériau magnétique, puis graver la matrice de polymère pour révéler les nanoparticules attachées au substrat. Si ce procédé est mené sur une couche sacrificielle, les particules peuvent être consécutivement mises en suspension. Les caractéristiques structurales et magnétiques de ces particules obtenues par auto-organisation du copolymère PS-PMMA seront étudiées, montrant que bien que ce procédé de fabrication soit encore à améliorer, il présente des avantages non négligeables en étant versatile, simple à mettre en œuvre et en permettant l’obtention de nanoparticules monodisperses et superparamagnétiques.Dans une seconde partie, un autre domaine biomédical sera abordé : le traitement du cancer. Une méthode nouvelle et alternative aux techniques d’hyperthermie ou de délivrance ciblée de médicaments avait été initiée par l’Argonne National Laboratory en 2010 et reprise à Spintec en 2011 : l’idée est de réactiver l’apoptose (ou mort programmée) de cellules cancéreuses par vibrations magnéto-mécaniques de microparticules magnétiques attachées à leur membrane. Il avait été démontré qu’avec des champs extérieurs aussi faibles que 30mT à 20Hz, des disques de permalloy en configuration magnétique vortex induisent l’apoptose de façon significative. Dans ce contexte et dans l’optique de pouvoir utiliser cette méthode pour des tests cliniques, des microparticules de magnétite, matériau biocompatible, ont été fabriquées par lithographie optique via le même procédé que les disques de permalloy. Leurs propriétés structurales, magnétiques et leur comportement en suspension sont comparés, ainsi que leurs effets sur les cellules in vitro via l’application d’un champ magnétique extérieur. A ce jour, les particules de permalloy sont supérieures en termes d’efficacité sur le déclenchement de l’apoptose des cellules cancéreuses. Certains paramètres du protocole tels que l’amplitude du champ doivent être optimisés pour les particules de magnétite, bien que les premiers effets observés soient encourageants pour la suite. / Magnetic nanoparticles are now used in a wide range of applications such as diagnostic, therapeutics or more recently theranostics. The numerous and diverse fabrication processes allow the fabrication of a wide range of nanoparticles in terms of size, shape, material and magnetic properties. An ideal fabrication process would allow the simple and cheap fabrication of a great quantity of monodisperse nanoparticles. In this objective, the first part of this work will be focused on a new and original fabrication process based on the combination of a “top-down” and “bottom-up” approach. The idea relies on the special auto organization properties of a diblock copolymer: one of the two phases has the ability to self organize into vertical cylinders in the matrix of the other polymer, provided that the annealing conditions are favourable. The selective etching of the cylinders leads to a mask of holes in a polymer matrix. Then, the deposit of a magnetic material and the etching of the polymer matrix leads to the formation of a hexagonal network of nanoparticles attached to the substrate. If the substrate is composed of a sacrificial layer, the nanoparticles can be released in a solution. The structural and magnetic properties of theses nanoparticles fabricated via a PS-PMMA template will be studied. Their characterization will show that the process is still to be optimized but allows already to obtain monodisperse superparamagnetic nanoparticles.A second part focuses on another biomedical applications of magnetic particles: the cancer treatment. A new technique, which is an alternative to the existing methods such as hyperthermia or drug delivery, was first proposed by the Argonne National Laboratory (2010) and taken over at Spintec (2011). The idea is to reactivate the apoptosis (programmed cell death) of cancer cells via the magneto mechanical vibrations of magnetic microparticles attached to their membranes. It was proved that weak external magnetic fields (30mT at 20Hz) applied on permalloy disks in a vortex configuration lead to a significant increase of the apoptotic rate of cancer cells. In the objective of making this method possible for clinical applications, biocompatible magnetite microparticles were fabricated via the same fabrication process than the permalloy disks (optic lithography). Their structural and magnetic properties are compared, as well as their behavior in a suspension and their lethal effect on cancer cells via the application of an external magnetic field. For now, the permalloy microdisks provide better results than the magnetite particles. Some parameters of the experimental set up have to be optimized for the magnetite particles, such as the amplitude of the applied magnetic field. However, the first effects observed with the magnetite particles are quite promising.

?rea de concentra??o: Produtos e coprodutos. / Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2018-06-22T19:43:47Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) barbara_goncalves_rocha.pdf: 2671242 bytes, checksum: 17dfa18bc6c5622c294695227a582c58 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2018-07-18T12:29:56Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) barbara_goncalves_rocha.pdf: 2671242 bytes, checksum: 17dfa18bc6c5622c294695227a582c58 (MD5) / Made available in DSpace on 2018-07-18T12:29:56Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) barbara_goncalves_rocha.pdf: 2671242 bytes, checksum: 17dfa18bc6c5622c294695227a582c58 (MD5) Previous issue date: 2018 / A diversifica??o da matriz energ?tica, por raz?es econ?micas, ambientais e da pr?pria pol?tica energ?tica das na??es, tem suscitado foco especial nos biocombust?veis, particularmente no bioetanol e no biodiesel. Na ind?stria, o biodiesel (?steres de ?cidos graxos com um ?lcool de cadeia molecular curta) ?, mais comumente, produzido pela transesterifica??o de triacilglicer?is de ?leos vegetais ou gordura animal, com metanol ou etanol, sob cat?lise homog?nea com uma base (KOH ou NaOH). Por representarem alternativas potencialmente mais sustent?veis, dos pontos de vistas econ?micos e ambientais, o presente trabalho foi dedicado a avaliar a efici?ncia qu?mica de catalisadores heterog?neos baseados em materiais de min?rios: (i) de ni?bio, enriquecido em Nb2O5 (Geo.Nb2O5); (ii) de areia monaz?tica (Geo.Mona), uma fonte mineral de terras raras, e (iii) de rejeitos de minera??o de fosfato, ricos em magnetita (Geo.Mag.CMT e Geo.Mag.CMA). Os materiais minerais foram preparados em mistura com componentes ?cidos (H2SO4; HCl ou HF) ou b?sicos (KOH; , KBr, NaOH; CaO; KI; KF ou KCl). As rea??es de transesterifica??o foram conduzidas sob refluxo, com ?leo de soja comercial e metanol, sob a??o dos catalisadores s?lidos. A raz?o molar padr?o ?leo:metanol foi de 1:100, com 10% de catalisador em rela??o ao ?leo, a 60 ?C. Dos testes realizados com os materiais preparados com CaO sint?tico comercial, nas mesmas condi??es, a mistura calcinada a 800 ?C por 4 h rendeu ?steres met?licos sempre acima de 99%; o menor tempo de rea??o (2 h, para completar a transesterifica??o) foi conseguido com o catalisador baseado na Geo.Mona, em rela??o ao Geo.Nb2O5 (5 h), ao Geo.Mag.CMT (3 h) e o Geo.Mag.CMA tamb?m (2 h). Analisou-se o reuso consecutivo do catalisador. Ap?s cada rea??o, o catalisador s?lido era lavado com metanol e seco a 100 oC. O melhor resultado foi obtido com o rejeito magn?tico com CaO calcinados a 200 ?C por 4 h, para o que se conseguiu at? 8 rea??es consecutivas. Nas impregna??es com ?cidos e bases, os melhores resultados foram com a mistura Geo.Nb2O5 e KOH calcinada a 600 ?C, para a qual conseguiu 8 rea??es consecutivas, com rendimento qu?mico em ?steres met?licos de praticamente 100% e tempo reacional de 10 min, no primeiro uso. O efeito catal?tico sin?rgico mais significativo foi conseguido com o catalisador baseado em cada um dos tr?s materiais avaliados em mistura com CaO: nenhum efeito catal?tico significativo na rea??o de transesterifica??o de triacilglcier?is do ?leo foi observado apenas com o material mineral puro calcinado. O CaO puro como catalisador, tamb?m calcinado e usado em rea??o, levou a rendimentos qu?micos pouco acima de 80%. A mistura individual do material mineral com CaO, nas mesmas condi??es de prepara??o anteriores, levaram a rendimentos qu?micos de efetivamente 100%. Os presentes resultados revelam a excepcional potencialidade, dos pontos de vista qu?mico, econ?mico e ambiental, dos catalisadores mistos, dos materiais minerais com CaO, ora avaliados, nos processos de produ??o industrial de biodiesel. / Tese (Doutorado) ? Programa de P?s-gradua??o em Biocombust?veis, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / The diversification of the energy matrix has been drawing special attention to biofuels, especially bioethanol and biodiesel, mainly for economic and environmental reasons and national energy policies. In industry, biodiesel (esters of fatty acids with a short-chain alcohols) is most commonly produced by the transesterification of triacylglycerols in vegetable oils or animal fats with methanol or ethanol using homogeneous catalysis with a base (KOH or NaOH). The present work was devoted to the evaluation of the chemical efficiency of heterogeneous catalysts based on mineral materials: (i) niobium, enriched in Nb2O5 (Geo.Nb2O5); (ii) monazite sand (Geo.Mona), a mineral source of rare earths, and (iii) phosphate mining tailings, rich in magnetite (Geo.Mag.CMT e Geo.Mag.CMA). The mineral materials were prepared in admixture with acidic (H2SO4, HCl or HF) or basic (KOH, KBr, NaOH, CaO, KI, KF or KCl) components. The transesterification reactions were conducted under reflux with commercial soybean oil and methanol in the presence of the solid catalysts. The standard molar ratio of oil:methanol was 1:100, using 10% catalyst relatively to the quantity of oil, at 60 ?C. According to the tests performed with the materials prepared with commercial synthetic CaO under the same conditions, the yield of methyl esters with the mixture calcined at 800 ?C for 4 h was always greater than 99%. The shortest reaction time (2 h to complete the transesterification) was achieved with the Geo.Mona catalyst; the reaction times with Geo.Nb2O5 (5 h), the Geo.Mag.CMT (3 h) and the Geo.Mag.CMA also (2 h) were longer. The consecutive reuse of the catalyst was also verified. After each reaction, the solid catalyst was washed with methanol and dried at 100 ?C. The best result was obtained with the magnetic waste with CaO calcined at 200 ?C for 4 h, with which up to eight consecutive reactions were achieved. On impregnating with acids or bases, the best results are obtained with the Geo.Nb2O5 and KOH mixture calcined at 600 ?C, with which eight consecutive reactions were completed. Virtually 100% yields of methyl esters were obtained in a reaction time of 10 min in the first use. The most significant synergistic catalytic effect was achieved with each of the three minerals mixed with CaO. No significant catalytic effect on the transesterification reaction of triacylglycerols in the oil was observed with the pure calcined minerals. When the calcined CaO is used alone as catalyst, the reaction yielded just over 80%. For the mixture of the individual minerals with CaO under the same preparation conditions described above, the transesterification reaction led to virtually 100% yields. The present results reveal an outstanding potential regarding the chemical, economic and environmental aspects of the mixed catalysts (the mineral material with CaO) for chemical processes leading to the industrial production of biodiesel.

Les bactéries magnétotactiques représentent un groupe d’une grande diversité écologique et phylogénétique. Elles sont capables de biominéraliser des nanocristaux de magnétite [un oxyde de fer (Fe(II)Fe(III)2O4)] ou de greigite [un sulfure de fer (Fe(II)Fe(III)2S4)] dans leurs magnétosomes, organites alignés en chaînes permettant la navigation le long des lignes de champ magnétique terrestre. Jusqu'à récemment, seules des souches produisant de la magnétite étaient disponibles en culture pure, conduisant à des études sur les mécanismes de biominéralisation de cet oxyde de fer. En 2011, une nouvelle bactérie capable de former de la magnétite et de la greigite, Desulfamplus magnetovallimortis souche BW-1, a été cultivée avec succès en laboratoire. Dans cette thèse, nous proposons d'utiliser une approche intégrée et multidisciplinaire pour comprendre les mécanismes de biominéralisation de la greigite en utilisant comme modèle d’étude la souche BW-1. Nous avons donc cherché à déterminer les conditions environnementales et biologiques favorisant la formation de la magnétite et de la greigite. Ces travaux ont également conduit à la caractérisation physiologique et phylogénétique de BW-1. Puis, l’utilisation d’approches globales et ciblées de transcriptomique ont permis d'évaluer le taux d'expression des gènes impliqués dans la formation des magnétosomes (magnétite vs. greigite) dans diverses conditions de croissance. Une approche de protéomique a permis d’apporter des informations supplémentaires à cette étude. Ces résultats ont permis de progresser dans la compréhension fondamentale de la biominéralisation in vivo, en particulier pour des bactéries formant de la greigite. / Magnetotactic bacteria represent a phylogenetically and ecologically diverse group of prokaryotes able to biomineralize magnetic nanocrystals composed of magnetite [an iron oxide (Fe(II)Fe(III)2O4)] or greigite [an iron sulfide (Fe(II)Fe(III)2S4)] in their magnetosomes, a prokaryotic organelle whose cytoplasmic alignement in chain allows the cell to navigate along the Earth’s magnetic field lines. Until recently, only magnetite-producing strains were available in pure culture. Thus, only the magnetite biomineralization has been studied. In 2011, a new bacterium able to form both magnetite and greigite, Desulfamplus magnetovallimortis strain BW-1, was isolated from Death Valley, California and cultivated in pure culture. In this work, we propose to use an integrated and multidisciplinary approach to understand the mechanisms involved in greigite biomineralization in BW-1 strain. First, we determined the environmental and biological conditions in which magnetite and greigite are formed. This first part of my thesis also contributed to the physiologic and phylogenetic characterization of this bacterium. Secondly, we used global and targeted transcriptomic approaches to evaluate the transcription levels of genes putatively involved in magnetosomes formation (magnetite vs. greigite) under various growth conditions. A proteomic approach provided additional informations to this study.Results obtained during my thesis contribute to the understanding of in vivo biomineralization, particularly for greigite production in magnetotactic bacteria.

A conjugação entre as nanopartículas (NPs) de diferentes materiais, por meio de ligações químicas entre as moléculas orgânicas presentes na superfície das NPs, pode produzir nanoestruturas core-satéllites multifuncionais com potenciais aplicações no campo biomédico. O objetivo deste estudo foi obter nanoestruturas core-satéllites ou conjugadas, com NPs de Fe3O4 e Au, por meio de reações químicas específicas entre moléculas orgânicas presentes nas superfícies das NPs. As NPs de Fe3O4 foram sintetizadas utilizando rotas de decomposição térmica, resultando em NPs com tamanho e forma controlados. O ácido oleico presente na superfície das NPs de Fe3O4, como sintetizadas, foi substituído pelos ligantes, 3-aminopropiltrimetoxisilano (APTMS) ou 3-mercaptopropiltrimetoxisilano (MPTMS). NPs de Au esféricas de 5,7 nm foram sintetizadas pelo método de Brust modificado, e a sua superfície foi modificada usando o ácido mercaptoundecanoico (AMU). A conjugação entre as NPs de Au e Fe3O4 foi realizada por duas vias diferentes. Primeiramente, usando os grupos amina-terminais livres das NPs Fe3O4@APTMS e os grupos carboxilatos das NPs Au@MUA e, depois, com a utilização dos grupos tióis das NPs Fe3O4@MPTMS e as NPs de Au, antes da modificação de superfície. Após a conjugação o comportamento superparamagnético das NPs de Fe3O4 foi preservado, mas a banda plasmon das NPs de Au apresentou um alargamento e um red-shift. Como esperado, a incorporação de materiais não magnéticos nas NPs magnéticas, resultou em uma pequena diminuição na magnetização de saturação em comparação com as NPs como sintetizadas. O alargamento observado na banda plasmon pode ser explicado pela agregação das NPs de Au, no entanto as influências magnéticas não podem ser discutidas. / The conjugation between nanoparticles (NPs) of different materials by using chemical bonds between organic molecules present on NPs surfaces can produce multifunctional core-satellites nanostructures and to provide potential applications in biomedical field. The aim of this study was to obtain core-satellites or conjugated nanostructures with Fe3O4 and Au NPs by specific reactions between organic molecules bonded on NPs surface. The Fe3O4 NPs were synthesized by using thermal decomposition routes leading to size-and shape-controlled NPs. As-synthesized Fe3O4 surface nanoparticles present oleic acid on surface, which was replaced by either (3-aminopropyl)trimethoxysilane (APTMS) or (3-mercaptopropyl)trimethoxylane (MPTMS) ligands. Spherical 5.7 nm Au NPs were synthesized by modified Brust method, and its surface was properly modified by using 11-mercaptoundecanoic acid (MUA). The conjugation between Au and Fe3O4 NPs was performed by two different routes. Firstly, using the free amine-terminal groups from Fe3O4@APTMS and the carboxylates groups from Au@MUA and, secondly, using thiols groups from Fe3O4@MPTMS and as-synthesized naked Au NPs. After conjugation, the superparamagnetic behavior of the Fe3O4 NPs was preserved, but the plasmon band has red-shifted and broadened. As expected the incorporation of non-magnetic materials onto the magnetic NPs, the saturation magnetization presents small decrease compared to as-synthesized NPs. Observed broadening in the plasmonic band can be explained by Au NPs aggregation, but the magnetic influences can not be discussed.

Submitted by ANA KARLA PEREIRA RODRIGUES (anakarla_@hotmail.com) on 2017-07-31T11:39:39Z No. of bitstreams: 1 arquivototal.pdf: 9429450 bytes, checksum: 4a660a5b5c0d6e333014749a35080084 (MD5) / Made available in DSpace on 2017-07-31T11:39:39Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 9429450 bytes, checksum: 4a660a5b5c0d6e333014749a35080084 (MD5) Previous issue date: 2016-07-28 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The present study develops bifunctional optical magnetic materials with high lantanide content. For this purpose, magnetite was pepared by co-precipitation method and chelating groups were introduced on the Fe3O4 surface with organosilanes containing ethylenediaminetetraacetic acid (EDTA) derivative, which were previously prepared via reaction between EDTA-dianhydride and aminoalkyl alkoxysilanes agents: 3- (Trimethoxysilyl)propylamine (1N), N-[3(trimethoxysilyl)propyl] ethylenediamine (2N) and N1-(3-trimethoxysilylpropyl)diethylenetriamine) (3N). After coordination of lanthanide ions (Gd3+, Eu3+, Tb3+ or Sm3+), the first coordination sphere of the lanthanide ions in the Ln-EDTA complexes, present on the modified surfaces of Fe3O4 particles, were completed by addition of -diketonate ligands (tta: thenoyltrifluoroacetonate, dbm: dibenzoylmetane, bzac: benzoylacetone and acac: acetylacetone) in order to improve their luminescence properties. The materials were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), wavelength dispersive X-ray fluorescence (WDXRF) and Fourrier-transform infrared spectroscopy (FT-IR) as well as by zeta potential measurements and luminescence spectroscopy. The hybrid materials exhibited intense red emission assigned to the 4f-4f transitions of the Eu3+ ion, likewise characteristic green and orange emissions of Tb3+ and Sm3+, respectively, indicating an efficient intramolecular ligand-to-metal energy transfer. The experimental intensity parameters ( 2 and 4), lifetimes (t), as well as radiative (Arad) and non-radiative (Anrad) decay rates of the Eu3+ ion were determined and discussed. / O presente trabalho desenvolve materiais bifuncionais óptico magnéticos contendo altos teores de íons lantanídeos. Para este propósito, a fase magnética foi preparada pelo método de coprecipitação e grupos quelantes foram introduzidos em sua superfície a partir da utilização de organosilanos derivados do ácido etilenodiamino tetra-acético (EDTA), os quais foram sintetizados previamente através da reação entre o dianidrido de EDTA (EDTA-DA) e os seguintes aminoalquil alcoxissilanos: 3-(Trimetoxissilil)propilamina (1N), N-[3(trimetoxissilil)propil]etilenodiamina (2N) e N1-(3-trimetoxissililpropil) dietilenotriamina. Após a coordenação do metal (Gd3+, Eu3+, Tb3+ ou Sm3+), a primeira esfera de coordenação dos íons lantanídeos nos complexos Ln-EDTA, presentes na superfície modificada das partículas de Fe3O4, foi complementada pela adição de ligantes -dicetonas (tta: tenoiltrifluoroacetona, dbm: dibenzoilmetano, bzac: benzoilacetona e acac: acetilacetona) com o objetivo de otimizar as propriedades luminescentes dos materiais. Os materiais foram caracterizados por difração de raios X de pós (XRD), magnetometria de amostra vibrante (VSM), microscopia eletrônica de varredura (SEM), microsopia eletrônica de transmissão (TEM), análise termogravimétrica (TGA), fluorescência de raios X por dispersão em comprimento de onda (WDXRF) e espectroscopia de absorção no infravermelho com transformada de Fourier (FTIR), bem como medidas de potencial zeta e espectroscopia de luminescência. Os materiais híbridos exibiram intensa emissão na cor vermelha, atribuída às transições 4f–4f do íon Eu3+ ion, da mesma forma que emissões na cor verde e laranja, características dos íons Tb3+ e Sm3+, respectivamente, indicando uma eficiente transferência de energia intramolecular do ligante para o metal. Os parâmetros de intensidade ( 2 e 4), o tempo médio de vida do estado emissor (t) e as taxas de decaimento radiativo (Arad) e não radiativo (Anrad) do íon Eu3+ foram determinadas e discutidas.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Conselho Nacional de Desenvolvimento Científico e Tecnológico / A região de Itutinga foi alvo de estudos prospectivos por parte da empresa BP mineração na década de 80, onde foram encontradas mineralizações em lentes de sulfetos metálicos (Zn-Cu-Ag-Fe) associados a rochas komatiíticas peridotíticas e basaltos toleíticos (anfibolitos) do greenstone belts, nas proximidades da fazenda São Jerônimo, enquadrando-se em um depósito do tipo VMS. A partir destas informações encontradas na literatura propôs-se estudar a estaurolita, a magnetita e a ilmenita para, a partir da determinação do seu conteúdo em zinco, indicar a aplicabilidade destes três minerais como traçadores desses tipos de depósitos. Para isso foram coletadas amostras de sedimentos de corrente e concentrados de batéia na região próxima à ocorrência, no entorno da cidade de Itutinga, e também em uma região próxima a cidade de Itumirim, já que existem semelhanças litológicas entre as duas áreas. Os sedimentos de corrente, as frações magnéticas e as frações de 0,3A (separador eletromagnético Frantz) foram enviados para análises químicas por absorção atômica e ICP-OES. Os concentrados de batéia foram descritos, separando-se cristais de estaurolita de cada amostra coletada, e analisando-os em MEV-EDS para determinação da química mineral. Os resultados dos sedimentos de corrente apontaram que os pontos da fazenda São Jerônimo (ME-03, Itutinga 51,7 ppm de Zn) e o ponto do Ribeirão Santa Cruz, (ME-06, Itumirim 36,1 ppm de Zn) foram os que apresentaram melhores resultados, indicando anomalias em zinco nas duas áreas estudadas . As estaurolitas, retiradas dos concentrados de batéia de cada ponto estudado, foram divididas em três conjuntos, de acordo com os teores de ZnO encontrados: 1 - entre 2,96% e 3,25% de ZnO em peso; 2 - entre 2,03% e 2,76% de ZnO em peso; 3 - < 1,67% de ZnO em peso, sendo comparável com outras estaurolitas encontradas em diversos depósitos de Zn do mundo, como Dry River, Austrália e Palmeirópolis Goiás. Assim, as estaurolitas apresentam bons resultados como minerais indicadores na área estudada. Em relação as magnetitas e ilmenitas estudadas, o número de amostras coletadas no presente estudo foram muito pequenas para se ter informações conclusivas sobre o papel destes minerais como traçadores. Por outro lado, os resultados das análises químicas nos concentrados de ilmenita (até 856 ppm de Zn) e nos concentrados de magnetita (até 216 ppm de Zn), indicam a disponibilidade deste metal nas áreas estudadas. Assim, é possível se detectar a presença do zinco por dois meios: através de sedimentos de corrente, através de halos de dispersão química do elemento zinco, e através dos minerais resistatos (estaurolita zincífera, magnetita e ilmenita), a partir de uma dispersão clástica do grão. / The Itutinga region was studied for BP mineration in 80s , where they found sulphide mineralization in lenses (Zn-Cu-Ag-Fe) associated with komatiitic peridotite rocks and tholeitic basalts (amphibolites) of greenstone belts, near of Fazenda São Jerônimo. With this information in the literature the propose is study the staurolite, magnetite and ilmenite for indicating the applicability of these three minerals as tracers of these types of mineralization. For this, samples of stream sediment and panning concentrates in the region near the city of Itutinga, and also in a region near the city of Itumirim. The stream current, magnetic fractions and ilmenite fractions were sent to chemistry analyses (Atomic absorption and ICP-OES), and the panning concentrates were analyzed for the separating of staurolite crystals, and sent to SEM-EDS. The stream sediments results showed that the point of Fazenda São Jerônimo (ME-03, Itutinga 51,7 ppm of Zn) and the point of Ribeirão Santa Cruz (ME-06, Itumirim 36,1 ppm of Zn) were presented the best result. The staurolite of panning concentrates were divided into three groups according to levels of ZnO matched: 1 - between 2.96% and 3.25% by weight of ZnO, 2 - from 2, 03% and 2.76% by weight of ZnO, 3 - <1.67% ZnO by weight, comparable with other staurolite found in many zinc deposits in the world, such as Dry River, Australia and Palmeirópolis Goiás. Thus, the staurolite show good results as indicator minerals in the area. With respect to magnetite and ilmenite concentrates, the number of samples collected in both areas was too small to have conclusive information. On the other hand, the results of the chemical ilmenite (up to 856 ppm Zn) and magnetite (up to 216 ppm Zn), indicate the availability of this metal in the areas studied. Thus, it is possible to detect the presence of zinc by two means: through stream sediments through chemical dispersion halos of zinc, minerals and through resistive minerals (zincian staurolite, magnetite and ilmenite), from a crystal clastic dispersion.